The 'smartphone' tomestone emote as an actual phone is kind of superflorous in the game's lore anyway as linkpearls already fill that role (they are literally phones in function, right down to using radio waves to transmit and recieve messages and having a phone-ringtone-like chirp in certain cutscenes when a npc is receiving a call.).

So I agree with Obsidian, the emote is basically just a tomestone reader and not an actual smartphone (I think we've kind of had enough smartphone placement in the FF series already with FFXV and it's ilk ), as linkpearls are already used for communication and serve the same purpose.